Optical fiber connectors that comprise a glass ferrule are known. See, for instance, U.S. Pat. No. 4,850,670. However, despite considerable potential cost advantage over conventionally used ceramic ferrules, glass ferrules have found only limited use, e.g., in the so-called rotary splice. This general failure to adopt an otherwise advantageous technology is caused at least in large part by the failure of many prior art glass ferrules to meet stringent strength requirements. Indeed, in the rotary splice there is only minimal mechanical stress on the glass ferrule since the rotary splice is assembled and not expected to be disassembled again.
In view of the significant cost savings that could result from the use of glass ferrules in optical fiber connectors, it would be highly desirable to have available glass ferrules having improved strength that can meet the strength requirements for optical fiber connectors.
U.S. Pat. No. 5,295,213 discloses a method of strengthening alkali-containing glass ferrules by ion exchange. The ion exchange method however is not applicable for vitreous silica or PYREX ferrules. On the other hand, it would be desirable to have available, for instance, vitreous silica ferrules that are strong enough for use in optical fiber connectors, since such ferrules can be produced relatively inexpensively with high dimensional accuracy, and will frequently be more abrasion resistant than the prior art alkali-containing glass ferrules.
This application discloses a method of strengthening glass ferrules and protecting the strength of the ferrules, including vitreous silica ferrules, and also discloses optical fiber connectors that comprise the strengthened glass ferrules.
Etching of silicate glass in hydrofluoric acid-based solutions is well known. See, for instance, G. A. C. M. Spierings, J. of Materials Science, Vol. 28, pp. 6261-6273 (1993); and D. J. Monk et al., Thin Solid Films, Vol. 232, pp. 1-12, (1993). It is also known that the mechanical strength of glass bodies, including silicate glass bodies, can be increased by etching. See, for instance, B. Proctor, Physics and Chemistry of Glasses, Vol. 3 (1), pp. 7-27, (1962); and L. A. Oriva et al., Soviet J. of Optical Technology, Vol. 46 (11), pp. 696-697, (1979). HF is a conventional silicate glass etchant, but other etchants (e.g., NaOH) are also known.